The present invention relates to a virtual accelerator for detecting an alarm condition within a pressurized gas sprinkler system, and a method thereof.
Known in the prior art is the dry pipe accelerator which is a hardware device that monitors a sprinkler system and activates the sprinkler system when a predetermined condition is met. For example, the condition is met when a significant rate of decay in system gas pressure occurs. The setting of the accelerator is factory set and cannot be changed by an operator. Furthermore, it is very difficult to coordinate the setting of the accelerator with the whole operation of the system.
Also known in the art is U.S. Pat. No. 5,236,049 in which is described an electronic fire reporting and sprinkling control module for connection to a control bus of a file alarm system. The control module is connected to a series of detectors. One of these detectors includes an air pressure switch which detects an air pressure drop in the sprinkler system. The switch provides an on or off signal corresponding to a such drop in pressure.
A disadvantage with the previous system is that the pressure switch has little flexibility because it is only restricted to two possible states of the sprinkler system, high pressure and low pressure.
Also known in the art is U.S. Pat. No. 5,971,080 in which is described a system for monitoring a rate of loss of pressure (dp/dt) in a dry pipe sprinkler. A comparison between the monitored rate of loss of pressure and a predetermined value is used to detect whether there is an open sprinkler head. Although the patent claims that the system is capable of accurately discriminating between false alarms, it is still susceptible to false alarms under normal operating conditions because no filtering of the monitored values is performed. Another drawback is that after the air compressor is turned off, the system is given a certain time to stabilize. During this time, the system cannot monitor the rate of loss of pressure and therefore cannot determine whether there is an open sprinkler head. Furthermore, the inherent presence of water in the dry pipe sprinkler and sudden changes in temperature foster changes in pressure that may lead to false alarms, especially after the compressor is turned off. Therefore, the system is ill equipped to deal with transient pressure changes that may occur during normal operating conditions of the dry pipe sprinkler and compressor.
Also known in the art, there are the following U.S. patents describing different sprinkler systems using a pressure detector having a predetermined threshold: U.S. Pat. Nos. 3,762,477; 3,888,314; 3,958,643; 4,356,868; 5,027,905; and 5,808,541. U.S. Pat. No. 4,570,719 describes a mechanical dry pipe accelerator.
Also known in the art, there are the following U.S. patents describing different fire extinguishing systems: U.S. Pat. Nos. 3,834,463; 3,949,812; 4,305,469; 4,356,868; 5,236,049; 5,653,291; 5,680,329; 5,915,480; 5,918,680; 5,927,406; 5,950,150. U.S. Pat. No. 4,401,976 describes an alarm system.
An object of the present invention is to provide a more sensitive accelerator than the above-mentioned previously known accelerators that distinguishes more efficiently between false alarms and real alarms.
According to the present invention, there is provided a virtual accelerator for detecting an alarm condition within a pressurized gas sprinkler system, comprising:
a pressure monitoring means for monitoring pressure within the pressurized gas sprinkler system, and generating a pressure signal representative of the pressure thereof;
sampling means for sampling the pressure signal at a given frequency during a predetermined period of time, and generating a series of pressure values; and
detecting means for detecting variations of the pressure values, and generating an alarm signal if the variations are within a predetermined range, the detecting means further comprising a low pass filter for low pass filtering the variations of the pressure values, and generating a first positive signal if the variations are within a low pass filter range.
Also, according to the present invention, there is provided a method for detecting an alarm condition within a pressurized gas sprinkler system, comprising the steps of:
(a) monitoring pressure within the pressurized gas sprinkler system, and generating a pressure signal representative of the pressure thereof;
(b) sampling the pressure signal at a given frequency during a predetermined period of time, and providing a series of pressure values; and
(c) detecting variations of the pressure values, and generating an alarm signal if the variations are within a predetermined range, the step of detecting variations further comprising the step of low pass filtering the variations of the pressure values, and generating a first positive signal if the variations are within a low pass filter range.